This invention relates to a V-type internal combustion engine, and more particularly to a V-engine for use in a marine propulsion system.
It has been found that placing a central exhaust manifold in the valley of a V-engine can substantially reduce the engine package size, as well as reduce stresses caused by mounting exhaust manifolds to the cylinder heads. Such a configuration is disclosed in copending patent application Ser. No. 07/118,863 filed Nov. 9, 1987. The disclosure of this copending application involves the use of induction pipes for introducing the air-fuel mixture to the engine from a point outside the valley of the V-engine. Upon proper selection of the length of the induction pipes, induction tuning can be achieved to boost the power output of the engine.
It has been found that further efficiencies can be achieved in the packaging of a V-engine by both providing air to the intake ports of the cylinders from within the valley of the V-engine, as well as by passing exhaust from the cylinders into the valley of the V-engine. The present invention is directed to a V-engine packaging for achieving such efficiencies. In accordance with the present invention, a four-stroke cycle V-engine includes a pair of cylinder banks, each of which has a plurality of cylinders. The cylinder banks are slanted with respect to each other to form a V-engine configuration. The upper end of each cylinder has an intake port for receiving an air-fuel mixture and an exhaust port for allowing exhaust to pass from the cylinder. Air intake means is disposed in the valley of the V-engine, and is in communication with the cylinder intake ports for supplying air thereto from within the valley of the V-engine. Exhaust collection means is also disposed in the valley of the V-engine. The exhaust collection means is in communication with the cylinder exhaust ports for passing exhaust therefrom. In one embodiment, the air intake means comprises an air intake manifold having a central air manifold and a plurality of passages which communicate between the central air cavity and the air intake ports. The exhaust collection means comprises an exhaust manifold having a central exhaust collection cavity and a single discharge at an end thereof. A plurality of exhaust passages are provided for communicating between the cylinder exhaust ports and the central exhaust collection cavity. The air intake manifold and the exhaust manifold are preferably disposed one above the other in the valley of the V-engine. In a preferred embodiment, the exhaust manifold is disposed below the air intake manifold. The exhaust manifold, as well as the exhaust passages, are preferably water jacketed to cool exhaust prior to its discharge from the central exhaust cavity of the exhaust manifold. With such water jacketing of the exhaust manifold, positioning the exhaust manifold below the air intake manifold places the heavier of the two components lower, thereby maintaining a low center of gravity for the engine package.
The invention also contemplates the provision of either a conventionally located cam shaft for operating the rocker arms which control the position of the valves for the intake and exhaust ports, or an overhead arrangement for the cam shaft.